Nat Mater. 2011 Mar;10(3):189-93. doi: 10.1038/nmat2958. Epub 2011 Feb 6.
The occupation of d orbitals controls the magnitude and anisotropy of the inter-atomic electron transfer in transition-metal oxides and hence exerts a key influence on their chemical bonding and physical properties. Atomic-scale modulations of the orbital occupation at surfaces and interfaces are believed to be responsible for massive variations of the magnetic and transport properties, but could not thus far be probed in a quantitative manner. Here we show that it is possible to derive quantitative, spatially resolved orbital polarization profiles from soft-X-ray reflectivity data, without resorting to model calculations. We demonstrate that the method is sensitive enough to resolve differences of ~3% in the occupation of Ni e(g) orbitals in adjacent atomic layers of a LaNiO(3)-LaAlO(3) superlattice, in good agreement with ab initio electronic-structure calculations. The possibility to quantitatively correlate theory and experiment on the atomic scale opens up many new perspectives for orbital physics in transition-metal oxides.
d 轨道占据控制着过渡金属氧化物中原子间电子转移的大小和各向异性，因此对其化学键和物理性质有重要影响。人们相信，表面和界面上的轨道占据的原子尺度调制是导致磁性和输运性质发生巨大变化的原因，但迄今为止，这种调制还无法以定量的方式探测到。在这里，我们展示了一种可以从软 X 射线反射率数据中推导出定量的、空间分辨的轨道极化分布的方法，而无需进行模型计算。我们证明，该方法的灵敏度足以分辨 LaNiO(3)-LaAlO(3) 超晶格中相邻原子层中 Ni e(g)轨道占据的差异约为 3%，与第一性原理电子结构计算结果非常吻合。在原子尺度上定量关联理论和实验的可能性为过渡金属氧化物中的轨道物理开辟了许多新的视角。
